1,3-Dibromo-5,5-dimethylhydantoin has been produced commercially. The product, as produced and sold, is in the form of a fine powder. Its principal use is as source of bromine in conducting bromination reactions in chemical syntheses.
Widely used as a biocidal agent for water are N,Nxe2x80x2-bromochloro-5,5-dialkylhydantoins. One of the features emphasized for such materials is that in use, the chlorine released from the biocide regenerates active bromine from inactive bromide species formed during the water treatment operation. In other words, the chlorine atom in the initial N,Nxe2x80x2-bromochloro-5,5-dialkylhydantoin is in effect regarded as a precursor for additional active bromine for sanitation purposes.
As is well known in the art, a deficiency of chlorine, of hypochlorites, and of certain halogenated organic water-treating agents is the formation during usage of undesirable disinfection by-products. These by-products are undesirable both from the standpoint of environmental concerns and also from the standpoint of toxicological considerations.
Although 1,3-dibromo-5,5-dimethylhydantoin is referred to in patent disclosures as one of a group of biocidal agents for water treatment, so far as is known, this compound in its pure or concentrated state has never achieved commercial use as a biocide in water treatment. Instead, in the prior art, only when in admixture with much larger quantities of N,Nxe2x80x2-bromochloro-5,5-dimethylhydantoin was 1,3-dibromo-5,5-dimethylhydantoin deemed suitable for use in water sanitation.
This invention is based on several new discoveries. First of all, one of us and some of our colleagues have discovered unexpectedly that 1,3-dibromo-5,5-dimethylhydantoin when used in treating water achieves the requirements of the U.S. Environmental Protection Agency at a dosage level that is only one-half of that required when using one or a mixture of N,Nxe2x80x2-bromochloro-5,5-dialkylhydantoins. This discovery enables the use of extremely small concentrations of the 1,3-dibromo-5,5-dimethylhydantoin to effectively sanitize water while at the same time achieving excellent microbiological control. Further, the ability to effectively utilize such small concentrations is expected to result in significant reduction in formation of disinfection by-products.
Moreover, it has also been discovered that 1,3-dibromo-5,5-dimethylhydantoin is also highly effective in combating biofilms which are microbiological slimes that form and prosper on surfaces in industrial and recreational water systems.
Such surprising and highly beneficial discoveries are more fully described in commonly-owned application Ser. No. 09/484,938 referred to above.
This invention involves, in part, the discovery was that samples of commercially-produced 1,3-dibromo-5,5-dimethylhydantoin particulate solids obtained from three different commercial sources could not be pressure compacted into shape-retentive tablets without use of a binder. All attempts to produce tablets without use of a binder resulted in utter failurexe2x80x94the compacted particles delaminated and broke into pieces during extraction from the die. Thus the commercially-produced 1,3-dibromo-5,5-dimethylhydantoin particulate solids could not be converted into tablets or briquettes, which are forms in which water treating biocides are commonly used, without first mixing the commercially-produced 1,3-dibromo-5,5-dimethylhydantoin particulate solids with a binding agent, commonly referred to as a binder.
Pursuant to this invention it has been further discovered, inter alia, that it is indeed possible to produce compacted forms of non-compactible 1,3-dibromo-5,5-dimethylhydantoin particulate solids without use of a binder. This can be accomplished by granulating non-compactible 1,3-dibromo-5,5-dimethylhydantoin particulate solids without use of a binder, and pressure compacting the granulated 1,3-dibromo-5,5-dimethylhydantoin, again without use of a binder.
Another embodiment of this invention is the provision of compacted articles such as granules, tablets, briquettes, and pucks produced, without use of a binder, using a process of this invention. In preferred forms, such articles have a crush strength of at least 15 pounds per inch, and typically in the range of 15 to 70 pounds per inch of thickness.
These and other embodiments and features of this invention will be still further apparent from the ensuing description and appended claims.
For ease of reference, the term xe2x80x9cnon-compactiblexe2x80x9d is used herein to denote that the given 1,3-dibromo-5,5-dimethylhydantoin particulate solids referred to cannot, without prior treatment to enhance its compactibility, be successfully converted into a shape-retentive tablet when subjected to the following conditions:
1) A 0.71 inch diameter circular die fabricated from Hastelloy(copyright) C alloy is lightly dusted with micronized polypropylene wax (MICROPRO 400 wax; Micro Powders, Incorporated, Tarrytown N.Y., or equivalent if MICROPRO 400 wax is not available).
2) A representative five-gram sample of the given 1,3-dibromo-5,5-dimethylhydantoin is manually placed into the above die.
3) The five-gram sample is pressure compacted in the die at 5000 psi using a Sintech(copyright) press (MTS Systems Corporation, Edenprairie, Minn.) equipped with a punch fabricated from Hastelloy(copyright) C alloy to form a 0.71-inch diameter circular tablet. No dwell time is used, i.e., the pressure is released just as soon as the pressure reaches 5000 psi.
4) If delamination or breakage occurs when the tablet is released from the die, the given 1,3-dibromo-5,5-dimethylhydantoin is deemed xe2x80x9cnon-compactible xe2x80x9d.
Conversely, the term xe2x80x9ccompactiblexe2x80x9d means that the 1,3-dibromo-5,5-dimethylhydantoin particulate solids referred to can be successfully converted into a shape-retentive tablet under the conditions just described in the immediately preceding paragraph.
This invention is applicable to both compactible and non-compactible 1,3-dibromo5,5-dimethylhydantoin. However, generally speaking it is preferred to utilize this invention with non-compactible 1,3-dibromo-5,5-dimethylhydantoin, since so far as is known, there is no other way of pressure compacting non-compactible 1,3-dibromo-5,5-dimethylhydantoin into a shape-retentive article in a die without use of a binder.
A preferred process of this invention comprises the following steps:
a) compressing compactible or, preferably, non-compactible 1,3-dibromo-5,5-dimethylhydantoin particulate solids in the absence of a binder into a sheet of a thickness in the range of about {fraction (1/16)} inch and about xc2xd inch;
b) subdividing such sheet into particles comprising particles in the range of about 80 mesh to about 3 U.S. standard mesh size, and preferably in the range of about 30 mesh to about 8 U.S. standard mesh size;
c) pressure compacting particles from b) in the range of about 80 mesh to about 3 U.S. standard mesh size, preferably particles in the range of about 30 mesh to about 8 U.S. standard mesh size, in a die in the absence of a binder mixed therewith.
Compression in a) can be conducted in any suitable press capable of applying suitable compression pressure, which typically is in the range of about 1000 to about 30,000 psi, and preferably in the ranger of about 5000 to about 25,000 psi. Preferred apparatus for such compression is a set of compression rolls. The resultant compressed shape, typically in the form of a sheet or other suitable breakable form, is then broken up into small granules in a suitable apparatus, such as, for example, in a Chilsonator(copyright) breaker (The Fitzpatrick Company, Elmhurst, Ill.). The particles in the size ranges referred to in b) are regarded as granulated 1,3-dibromo-5,5-dimethylhydantoin: If in b) particles are also formed that are larger and/or smaller than the selected size referred to in b), it is preferred to classify the particles formed in b) into (1) a fraction containing the particles in the selected size range of b), and (2) either or both of (i) a fraction composed of the larger particles, and/or (ii) a fraction composed of the smaller particles, as the case may be. Where a fraction of (i) exists, such fraction is preferably recycled to b). Where a fraction of (ii) exists, such fraction is preferably recycled to a).
If desired, the surfaces of the die used in c) may be lubricated with a suitable lubricant to facilitate removal of the compacted article from the die. However, as noted, no binder is used in this operation or for that matter, none is used in step a) either.
The time period during which the pressure is applied to the 1,3-dibromo-5,5-dimethylhydantoin solids in a) and in c) is not critical. As long as suitable compaction is achieved, the time of compaction is of little or no consequence. In any situation where the optimum time has not been previously determined, a few simple preliminary tests should readily enable such pressure conditions, including pressure times, to be determined and optimized.
The compaction or compression steps in a) and c) above are typically initiated with the 1,3-dibromo-5,5-dimethylhydantoin solids at room temperature. However, if desired, the solids can be preheated or precooled such that the compaction or compression is initiated at a temperature in the range of about 5 to about 80xc2x0 C.
If desired, the 1,3-dibromo-5,5-dimethylhydantoin particulate solids can be formulated with suitable excipients such as disintegrants, lubricants, and mold release agents. Other optional ingredients which may be used in the formulation of products from the 1,3-dibromo-5,5-dimethylhydantoin particulate solids include fragrances, stabilizers, corrosion inhibitors, dyes, other biocidal agents, surfactants, effervescents, diluents, builders, chelating agents, and the like. Such ancillary materials should of course be compatible with 1,3-dibromo-5,5-dimethylhydantoin and not interfere in any material way with the excellent performance characteristics of the 1,3-dibromo-5,5-dimethylhydantoin particulate solids of this invention. The amount(s) of such ancillary materials used should of course be sufficient to serve the purpose for which it is, or they are, being used. At the same time, the amount used should not materially detract from the physical, mechanical, or performance properties of the formulated product.